Problem: Michael is 3 times as old as William and is also 14 years older than William. How old is Michael?
Solution: We can use the given information to write down two equations that describe the ages of Michael and William. Let Michael's current age be $m$ and William's current age be $w$ $m = 3w$ $m = w + 14$ Now we have two independent equations, and we can solve for our two unknowns. One way to solve for $m$ is to solve the second equation for $w$ and substitute that value into the first equation. Solving our second equation for $w$ , we get: $w = m - 14$ . Substituting this into our first equation, we get the equation: $m = 3$ $(m - 14)$ which combines the information about $m$ from both of our original equations. Simplifying the right side of this equation, we get: $m = 3m - 42$ Solving for $m$ , we get: $2 m = 42$ $m = 21$.